CONTROLLING BACTERIA NATURALLY

Bacteria occurs naturally. It is nature's system for converting waste to nutrients. When waste builds up beyond a system's ability to convert it the bacteria will overwhelm the system. This occurs from overfeeding but it also occurs when the substrate becomes loaded with waste.
Gravel systems always produce bacteria that thrives in the water column. Sand systems keep the bacteria in the substrate un til the waste overwhelms the ability of the deep sandbed to break down waste into nutrients that are taken up by the roots of plants. When this occurs the waste becomes a channel for O2 and the anaerobic layer is destroyed.
The solution is very simple. Add more sand to recreate the anaerobic layer. O2 can only permeate about 2" into the sand unless the sand becomes loaded with waste. Then all bets are off and the anaerobic can no longer do its job. Fix it by adding an inch or 2 of sand and things will get back to normal very quickly.